首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   501篇
  免费   23篇
林业   57篇
农学   15篇
基础科学   2篇
  107篇
综合类   63篇
农作物   29篇
水产渔业   29篇
畜牧兽医   176篇
园艺   5篇
植物保护   41篇
  2023年   4篇
  2022年   7篇
  2021年   12篇
  2020年   10篇
  2019年   11篇
  2018年   10篇
  2017年   11篇
  2016年   10篇
  2015年   12篇
  2014年   16篇
  2013年   25篇
  2012年   38篇
  2011年   41篇
  2010年   28篇
  2009年   29篇
  2008年   35篇
  2007年   27篇
  2006年   28篇
  2005年   34篇
  2004年   24篇
  2003年   26篇
  2002年   26篇
  2001年   6篇
  2000年   6篇
  1999年   2篇
  1998年   6篇
  1997年   1篇
  1996年   4篇
  1995年   4篇
  1994年   5篇
  1993年   4篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1986年   2篇
  1985年   1篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1976年   1篇
  1974年   1篇
  1971年   3篇
  1970年   2篇
  1968年   2篇
  1961年   1篇
排序方式: 共有524条查询结果,搜索用时 0 毫秒
521.
Molecular genetics has revealed a precise stereotypy in the projection of primary olfactory sensory neurons onto secondary neurons. A major challenge is to understand how this mapping translates into odor responses in these second-order neurons. We investigated this question in Drosophila using whole-cell recordings in vivo. We observe that monomolecular odors generally elicit responses in large ensembles of antennal lobe neurons. Comparison of odor-evoked activity from afferents and postsynaptic neurons in the same glomerulus revealed that second-order neurons display broader tuning and more complex responses than their primary afferents. This indicates a major transformation of odor representations, implicating lateral interactions within the antennal lobe.  相似文献   
522.
The Born-Oppenheimer approximation of uncoupled electronic and nuclear motion is a standard tool of the computational chemist. However, its validity for molecule-metal surface reactions, which are important to heterogeneous catalysis, has been questioned because of the possibility of electron-hole pair excitations. We have performed experiments and calculations on the scattering of molecular hydrogen from a catalytically relevant metal surface, obtaining absolute probabilities for changes in the molecule's velocity parallel to the representative Pt(111) surface. The comparison for in-plane and out-of-plane scattering and results for dissociative chemisorption in the same system show that for hydrogen-metal systems, reaction and diffractive scattering can be accurately described using the Born-Oppenheimer approximation.  相似文献   
523.
We report that the organic salt (EDO-TTF)2PF6 with 3/4-filled-band (1/4-filled in terms of holes), which forms an organic metal with strong electron and lattice correlation, shows a highly sensitive response to photoexcitation. An ultrafast, photoinduced phase transition from the insulator phase to the metal phase can be induced with very weak excitation intensity at near room temperature. This response makes the material attractive for applications in switching devices with room-temperature operation. The observed photo-induced spectroscopic change shows that this photoinduced phase transition process is caused by the cooperative melting of charge ordering assisted by coherent phonon generation.  相似文献   
524.
PRACTICAL RELEVANCE: Feline trauma is commonly seen in general practice and frequently involves damage to the head. CLINICAL CHALLENGES: While craniofacial injuries following trauma vary widely in severity, affected cats can often be severely compromised in terms of their neurological, respiratory and cardiovascular status, and their management can be challenging in both the short and long term. They need prompt stabilisation and careful monitoring in the initial period to maximise prospects of a successful outcome. Many cats with severe facial trauma will require surgery to stabilise skull fractures or address injuries to the eyes, with its inherent issues surrounding pain management, ensuring adequate nutrition and the necessity for ongoing hospitalisation. DIAGNOSTICS: Cats with head trauma benefit from imaging of the injured areas as well as thoracic radiography. Imaging the skull can be challenging and is best performed under general anaesthesia. In unstable patients this can be delayed to prevent any associated morbidity. EVIDENCE BASE: The clinical evidence base relating to injury to the feline head is limited, despite its relative frequency in general practice. This review focuses on the initial approach to craniofacial (in particular, ocular and jaw) trauma, and outlines simple techniques for management of soft tissue and bone injuries. Much of the information is based on the authors' clinical experience, as there is a paucity of well-described clinical case material.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号